Thursday, 7 July 2016

A Little more practice needed

So tonight I decided to have a little play with the Lathe. I probably should've gone to bed early for work tomorrow. but it was calling me.
You may remember that I am setting up a fixture on my mill to experiment with parts drawn in Fusion 360 then exported through to it. Unfortunately as you can see in the above picture the hold down bolts I have are a little too long. To fix this I could cut them down with the hacksaw. But I thought it would be a lot cooler and good experience to use the lathe.
So I set everything up as near as I could figure to correct.
I put a little oil on the part. I was planning to add a drop halfway through, but the spindle doesn't run with the face shield up so I had to put a drop on then just let it go. Probably not too big of a concern with this part at it's fairly small and although it will produce some heat it shouldn't get too bad.
The result of the first pass. The spindle started to load up a little then the tool seemed to jump over the little nipple that was left without actually cutting through it. So perhaps the tool is too high? Simple solution, lower it then.
Hmmm. Possibly too low. This picture looks much worse than it did in real life.
Here we go. I did add another drop of oil, but it had pretty much been thrown off by the time the tool came in, I probably won't worry in the future.
It worked. Kinda. It's a bit difficult to see in the pictures. But the surface finish on the part in the chuck isn't great and while it did cut through it wasn't particularly happy about it.

I thought it must be too low now so I moved everything around again and had another crack at this. Just for practice now.
Unfortunately this attempt was an unmitigated disaster. The tool got caught in the threads and was deflected off to the side. Then it started to cut. Thankfully I stopped the machine before anything snapped.
The Solution? Turned out not but it was a fun thing to try. I set up another tool opposite the parting tool. This is more or less how the machine was when I received it. I wish now that I'd played around more as it was. But hindsight is 20/20 and I knew even less then than I do now. However I was able to turn this to a fairly good surface finish quite easily.
The feed was set at about 10mm/min, the depth of cut was about what looked pretty good and the spindle was set at 1/4 of the way between 200 and 2000 on the dial for it. Not sure how accurate that is though.

So now that we have a nice flat surface that isn't going to deflect the tool lets try again.
This was the result. The tool just rubbed and pushed the workpiece around. It actually crushed some of the threads in the chuck so the steppers at least have a bit of go to them even if the spindle is a bit weak.

At this point I decided to call it a night and had a quick look at the turning insert I was using.
Thankfully no visible damage as I expected. However it is always good to double check.

I will probably go back to playing with the wax and delrin(?) blanks I have for a little while, at least until I get a better feel for how each of the tools work and getting them set properly. The good news there is that means I will probably get to the mill sooner again. I will rig up a fan that actually works to send some air over the stepper drivers as they do get quite hot although I think they are still just within spec for passive cooling. Then once that's done, I have worked out a method for driving the spindle so it will be full speed ahead for making some chips over there too.

Cheers,
Rex